For the purpose of sound absorption in aircraft interiors sandwich panels are used that comprise a honeycomb core as a core structure with cover layers on both sides. The honeycomb core is, for example, formed using Nomex® paper that is impregnated with phenolic resin, while the cover layers are made from a fibre-reinforced plastic material, in particular from a so-called prepreg material. The term “prepreg” material refers to woven reinforcement-fibre fabrics, interlaid reinforcement-fibre scrims or reinforcement fibres that have been pre-impregnated in the factory with a suitable resin system, for example an epoxy resin or the like, and that are subsequently cured at suitable temperatures and pressures without any further additives such as, for example, hardeners. The interlaid reinforcement-fibre scrim, the woven reinforcement-fibre fabric and the reinforcement fibres can, for example, comprise carbon fibres, glass fibres, aramide fibres or the like. However, such sandwich panels do not provide gas permeability to an extent worth mentioning.
Furthermore, sound absorption elements are known in which a layer of sound absorption material is arranged between perforated metal sheets or the like. The weight per unit of area of such structures is, as a rule, too heavy for applications in aircraft engineering.